The lymphocyte hybridoma technique will be used to obtain monospecific antibodies against prostatic carcinoma-specific antigens employing the established prostatic carcinoma cell lines DU145 and PC3, cell suspensions from heterotransplants of these cell lines, or fresh prostate tumor tissue as immunogens. The production and specificity of the antibody secreting hybridomas will be monitored by a radioimmune cell-binding assay using a panel of cultured and fresh human normal and tumor cells. Clones secreting antibody specific to prostatic carcinoma cells will be maintained as ascites in BALB/c mice. The monospecific antibody will be used to prepare immunoabsorbents for purification of the prostatic carcinoma-specific antigen in 3M KCl extracts of prostatic tumor cells by biospecific affinity chromatography. Purification of the specific antigen will be monitored by gel electrophoresis, immunoelectrophoresis, and in vitro binding immunoassays. Physicochemical characterization and determination of whether the purified tumor specific antigen-cross reacts with prostatic acid phosphatase, oncofetal antigens, and HLA antigens will be performed using established procedures. The purified antigen and monospecific antibody will be used to develop a radioimmunoassay, and the potential value of this assay for diagnosis and monitoring of prostatic cancer patients before and after therapy will be assessed.